Vasoocclusion devices are surgical instruments that are placed within vessels, typically via a catheter, to block the vessel or to fill a vascular cavity such as an aneurysm. One type of vasoocclusion device is in the form of a helical wire coil. See U.S. Pat. No. 4,994,069. The coil may be placed at the desired site in several ways. One involves loading the coil into the lumen of a catheter whose distal end is located at the site. The coil is then advanced through the catheter lumen using a pusher and expelled from the distal end of the catheter. Another involves detachably coupling the coil to the distal end of a wire, advancing the assembly to the site using a catheter, and uncoupling the coil from the wire at the site. U.S. Pat. Nos. 5,234,437; 5,250,071; 5,261,916; 5,304,195; 5,312,415; and 5,350,397 describe coils that are detachably coupled to a wire.
Detachable coils carry a member on their proximal end that detachably engages or interlocks with a member on the distal end of the wire. A problem experienced with such coils is that the member carried on the coil is oriented tangentially to the helical diameter of the coil. As such, when the coil is decoupled, the member extends tangentially outwardly from the helix diameter and may engage the vessel wall. (See FIG. 1 of the drawings) Such engagement may injure or even perforate the vessel wall.
A principal object of this invention is to provide a detachable helical vasoocclusive coil in which the member that attaches to the wire is not oriented tangentially to the diameter of the coil. Accordingly, the coils of this invention are less likely to injure the vessel wall.